PROJECT SUMMARY/ABSTRACT This application proposes a customized research training plan designed to promote the development of the applicant into an independent investigator. The plan includes advanced training in laboratory experimentation, along with tailored professional and career development opportunities. The training plan is supported by the outstanding availability of local and institutional resources at UIC. The proposed research will examine cellular communication mechanisms that control scar formation, a common result of the healing response. In most tissues, the end result of tissue repair is a fibrous scar containing altered amounts and structure of the extracellular matrix components. Scarring and fibrosis occurs in numerous tissues and can create serious functional problems such as limited mobility, restricted skeletal growth, and weakened tissue strength that may lead to wound dehiscence. In the craniofacial region, scarring can impair both functionality as well as appearance, leading to a variety of physiologic and psychologic problems. Robust angiogenesis, a prominent feature of wound repair, includes the creation and then pruning of vessels. Angiogenesis is associated with increased fibrosis in numerous tissues including skin, lung, and liver. The goal of the proposed studies is to examine how the endothelial cells that arise during wound angiogenesis communicate with surrounding fibroblasts and how they influence their function and subsequent collagen deposition. One way that endothelial cells might communicate with fibroblasts is via small extracellular vesicles, called exosomes. The research plan utilizes traditional wound healing assays, methods for exosome purification and application, and small RNA and RNA sequencing tools to study exosome-mediated communication between these two cell types and to identify the resultant phenotypic changes in fibroblast activity. The central hypothesis of this research is that exosomes secreted from endothelial cells influence the phenotype of fibroblasts during wound healing and fibrosis. Our long-term goal is to understand how communication between endothelial cells and fibroblasts affects the scarring phenotype. Aim 1 will examine the effects of endothelial cell exosomes on fibroblast activity and fibrosis in vitro and in vivo. In vitro wound healing assays will be employed, and fibroblasts exposed to endothelial cell exosomes will be assessed for changes in migration, cell cycle phase, proliferation, and gene expression. An in vivo mouse model will be used to assess fibrosis and collagen architecture after intradermal injection on endothelial cell exosomes. Aim 2 will utilize bioinformatics tools to identify and characterize the specific miRNA cargo of endothelial cell exosomes that is mostly likely to impact fibroblast function at sites of scarring and fibrosis. Together, the Aims will lead to a better understanding of the mechanisms by which endothelial cells might modulate fibroblast function, and may lead to the development of novel therapeutics to treat fibrotic diseases.